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Abstract:

A flue gas treatment process and system is presented. The system includes
a fan capable of moving a flue gas through a flue gas desulfurizer,
direct contact cooler, and CO2 absorber, without the need for a
booster fan. The system also includes a direct contact cooler and CO2
absorber that are configured to withstand gas conditions present at the
flue gas desulfurizer exit. When the direct contact cooler and CO2
absorber are shutdown, the speed of the fan is lowered and the flue gas
continues to flow through the cooler and CO2 absorber and out a chimney.
The overall cost of installing, operating, and maintaining the system is
lower than that of conventional processes and systems.

Claims:

1. A post-combustion flue gas treatment system comprising: a flue gas
desulfurizer configured to remove SO2 from flue gas passing through
the desulfurizer and to produce desulfurized flue gas; a direct contact
cooler fluidly connected to, and downstream from, the flue gas
desulfurizer via a first conduit, wherein the cooler is configured to
cool the desulfurized flue gas passing through the cooler to produce a
cooled desulfurized flue gas; a CO2 absorber fluidly connected to,
and downstream from, the direct contact cooler via a second conduit,
wherein the absorber is configured to remove CO2 from the cooled
desulfurized flue gas passing through the absorber; a fan fluidly
connected to the desulfurizer and configured to provide sufficient
pressure to move flue gas through the desulfurizer, contact cooler, and
absorber without the need for a second fan; and wherein the direct
contact cooler, CO2 absorber, and first and second conduits are
configured to withstand desulfurized flue gas conditions that are present
at an exit of the desulfurizer.

2. The system of claim 1, further comprising a boiler fluidly connected
to the desulfurizer, and wherein the fan is located in the fluid pathway
connecting the boiler and the desulfurizer.

3. The system of claim 1, wherein the fan is located in the second
conduit.

4. The system of claim 1, where in the desulfurized flue gas conditions
comprises a temperature of at least 120.degree. F., an acidity of at
least 5 pH, and a humidity of at least 50%.

5. The system of claim 1, where in the desulfurized flue gas conditions
comprises a temperature of at least 180.degree. F., an acidity of at
least 2 pH, and a humidity of at least 90%.

6. The system of claim 1, further comprising a chimney fluidly connected
to the absorber.

7. A gas treatment system comprising: a first gas conditioning unit
configured to (i) remove a first constituent from a gas passing through
the first gas conditioning unit and (ii) produce a substantially
first-constituent-free gas; a second gas conditioning unit fluidly
connected to, and downstream from, the first gas conditioning unit via a
first conduit, wherein the second gas conditioning unit is configured to
(i) modify a property of the substantially first-constituent-free gas
passing through the second gas conditioning unit and (ii) produce a
modified substantially first-constituent-free gas; an absorber fluidly
connected to, and downstream from, the second gas conditioning unit via a
second conduit, wherein the absorber is configured to remove a second
constituent from the modified substantially constituent-free gas passing
through the absorber; a fan fluidly connected to the first gas
conditioning unit and configured to provide sufficient pressure to move a
gas through the first gas conditioning unit, second gas conditioning
unit, and absorber without the need for a second fan; and wherein the
second gas conditioning unit, absorber, and first and second conduits are
configured to withstand gas conditions that are present at an exit of the
first gas conditioning unit.

8. The gas treatment system of claim 7, wherein the first constituent
comprises a sulfur oxide.

9. The gas treatment system of claim 7, wherein the property is selected
from the group consisting of density, temperature, and pressure.

10. A method of operating a plant comprising: adjusting a speed or vane
position of a fan as a function of an operational parameter of a direct
contact cooler and a CO2 absorber; and wherein the fan is configured
to provide sufficient pressure to move a flue gas through a desulfurizer
fluidly connected to the direct contact cooler and CO2 absorber
without the need for a second fan, when the direct contact cooler and
CO2 absorber are in an operational state.

11. The method of claim 10, wherein the direct contact cooler and CO2
absorber are configured to withstand a gas condition at an exit of the
desulfurizer.

12. A method of simplifying a plant comprising; configuring a first fan
to provide sufficient pressure to move a flue gas through a flue gas
desulfurizer, direct contact cooler, and CO2 absorber, without the
need for a second fan; configuring the direct contact cooler and CO2
absorber to withstand flue gas conditions present at an exit of the flue
gas desulfurizer; optionally removing a second fan fluidly connected to
the flue gas desulfurizer, direct contact cooler, and CO2 absorber;
and optionally removing a bypass conduit fluidly connecting the flue gas
desulfurizer to a chimney.

Description:

[0001] This application claims the benefit of priority to application Ser.
No. 61/484856, filed on May 11, 2011. This and all other extrinsic
materials discussed herein are incorporated by reference in their
entirety. Where a definition or use of a term in an incorporated
reference is inconsistent or contrary to the definition of that term
provided herein, the definition of that term provided herein applies and
the definition of that term in the reference does not apply.

FIELD OF THE INVENTIVE SUBJECT MATTER

[0002] The field of the inventive subject matter is post-combustion flue
gas treatment, more specifically, CO2 capture and removal from flue
gases.

BACKGROUND

[0003] Fossil fuel combustion is an important source of power generation,
and provides a major portion of the world's power demands. Unfortunately,
fossil fuel combustion is also a major contributor of pollutants to the
atmosphere and environment. The exhaust gases that result from burning
fossil fuels, called "flue gases," contain many harmful air pollutants,
such as nitrogen oxides, sulfur dioxide, carbon dioxide, volatile organic
compounds and heavy metals.

[0004] Various environmental regulations mandate treatment of flue gas,
such as sulfur dioxide (SO2) and carbon dioxide (CO2) capture
and removal. These treatment processes can greatly increase the cost of
power production, resulting in higher prices to the consumer. Improved
techniques, processes, and devices for treating flue gases help to
control and reduce the increasing costs of power production.

[0005] U.S. Pat. No. 7,255,842 to Yeh teaches a process for removing
sulfur oxides, nitrous oxides, and carbon dioxide from flue gases without
producing harmful byproducts and while achieving low energy consumption.
While Yeh appreciates the need to reduce operational costs, Yeh fails to
appreciate that the net costs of building, operating, and maintaining a
power plant can be lowered despite a moderate raise in operational costs.
Of particular importance to the present application, Yeh fails to
appreciate that a single fan system consuming high amounts of energy can
actually reduce overall costs compared to a system that utilizes two fans
that consume a lower amount of energy than the single fan.

[0006] There is still a need for improved processes and systems for
post-combustion treatment of flue gases that reduce the net costs of
power production.

SUMMARY OF THE INVENTIVE SUBJECT MATTER

[0007] The inventive subject matter provides apparatus, systems and
methods in which a post-combustion flue gas treatment system is
simplified by eliminating various components, such as fans, bypass
conduits, and related components.

[0008] In one aspect of some embodiments, the system includes a boiler,
flue gas desulfurizer (FGD) unit, direct contact cooler (DCC) unit,
CO2 absorber, and chimney, all fluidly connected. The FGD unit is
configured to remove SO2 from flue gas passing through the
desulfurizer to produce desulfurized flue gas. The DCC unit is configured
to cool the desulfurized flue gas passing through the cooler to produce a
cooled desulfurized flue gas. The CO2 absorber is configured to
remove CO2 from the cooled desulfurized flue gas passing through the
absorber to produce a treated gas that has reduced amounts of CO2
and SO2. A fan is fluidly connected to the FGD unit and is
configured to provide sufficient pressure to move flue gas through the
FGD unit, DCC unit, CO2 absorber, and chimney without the need for a
second fan.

[0009] In another aspect of some embodiments, the DCC unit, CO2
absorber, and all the conduits located downstream from the FGD unit are
configured to withstand desulfurized flue gas conditions that are present
at an exit of the FGD unit. The desulfurized flue gas conditions can
comprise a temperature in the range of 120° F.-250° F., an
acidity in the range of 1-5 pH, and a humidity in the range of 50%-100%.
However, desulfurized flue gas conditions exceeding those ranges are also
contemplated.

[0010] Unless the context dictates the contrary, all ranges set forth
herein should be interpreted as being inclusive of their endpoints and
open-ended ranges should be interpreted to include commercially practical
values. Similarly, all lists of values should be considered as inclusive
of intermediate values unless the context indicates the contrary.

[0011] In some embodiments, the fan is located in the fluid pathway
connecting the boiler and the desulfurizer. In other embodiments, the fan
is located in the conduit connecting the DDC unit and the CO2
absorber.

[0012] From a methods perspective, the inventive subject matter provides a
method of operating a power plant comprising adjusting a speed or vane
position of a fan as a function of an operational parameter (e.g., on or
off) of a direct contact cooler and a CO2 absorber. The fan provides
sufficient pressure to move flue gas through the desulfurizer fluidly,
direct contact cooler, and CO2 absorber when the direct contact
cooler and CO2 absorber are in an operational state, without the
help of a second fan. The method can further include the step of
modifying the direct contact cooler and CO2 absorber to better
withstand the gas conditions present at the desulfurizer exit.

[0013] In other aspects, the inventive subject matter provides a method of
simplifying a power plant comprising: (i) configuring a first fan to
provide sufficient pressure to move a flue gas through a flue gas
desulfurizer, direct contact cooler, and CO2 absorber, without the
need for a second fan; (ii) configuring the direct contact cooler and CO2
absorber to withstand flue gas conditions present at an exit of the flue
gas desulfurizer; (iii) optionally removing a second fan fluidly
connected to the flue gas desulfurizer, direct contact cooler, and
CO2 absorber; and (iv) optionally removing a bypass conduit fluidly
connecting the flue gas desulfurizer to a chimney.

[0014] Various objects, features, aspects and advantages of the inventive
subject matter will become more apparent from the following detailed
description of preferred embodiments, along with the accompanying drawing
figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

[0015] FIG. 1 is a schematic of a flue gas treatment process with two fans
and a bypass conduit.

[0016] FIG. 2 is a schematic of a flue gas treatment process that has only
one fan and no bypass conduit.

[0017] FIG. 3 is a schematic of another embodiment of a flue gas treatment
process with only one fan and no bypass conduit.

[0018] FIG. 4 is a schematic of a flue gas treatment process that has one
fan and a bypass conduit.

DETAILED DESCRIPTION

[0019] One should appreciate that the disclosed techniques provide many
advantageous technical effects including reducing costs for power
production processes and systems.

[0020] The following discussion provides many example embodiments of the
inventive subject matter. Although each embodiment represents a single
combination of inventive elements, the inventive subject matter is
considered to include all possible combinations of the disclosed
elements. Thus if one embodiment comprises elements A, B, and C, and a
second embodiment comprises elements B and D, then the inventive subject
matter is also considered to include other remaining combinations of A,
B, C, or D, even if not explicitly disclosed.

[0021] FIG. 1 shows a post-combustion flue gas treatment system 100, which
is capable of capturing and removing SO2 and CO2 from flue
gases. System 100 comprises an induced draft fan 110 downstream from a
boiler (not shown) and upstream from a flue gas desulfurizer (FGD) 120.
Fan 110 is configured to move flue gas from the boiler (not shown) into
the FGD 120. Fan 110 is also configured to move flue gas from FGD 120 and
out of system 100 into the atmosphere via bypass conduit 125 and chimney
170 when damper 133 is closed and damper 123 is open. However, when
damper 123 is closed and damper 133 is open, fan 110 is not configured to
provided sufficient pressure to move the flue gas into direct contact
cooler (DCC) 130.

[0022] FGD 120 is configured to remove SO2 from the flue gas as the
flue gas passes through it. Various desulfurizer configurations are known
in the art. Examples of desulfurizers can be found in U.S. Pat. Nos.
7,524,470, 7,625,537, 6,936,231, 7,052,662, 7,048,899, 6,991,771,
6,605,263, 6,132,692, and U.S. Patent Application Publication Nos.
2004/0105802, 2003/0175190, 2003/0108472, 2003/0108469, 2003/0108466,
which are all incorporated herein by reference. FGD 120 can be configured
in any fashion that is suitable for removing at least some SO2 from
the flue gas. The particular configuration of FGD 120 is not intended to
limit the inventive subject matter taught herein. In some embodiments,
the FGD unit is configured to produce a gas that is substantially free of
SO2.

[0023] Direct contact cooler (DCC) 130 is fluidly connected to FGD 120 via
conduit 135. DCC 130 is configured to prepare flue gases for CO2
removal by decreasing the flue gas temperature, thus increasing flue gas
density. A booster fan 140 is located just downstream of DCC 130 and
upstream of CO2 absorber 150. Due to the pressure resistance in DCC
130 and absorber 130, fan 140 is included in order to pull flue gas out
of DCC 130 and into absorber 150. Fan 140 then pushes the flue gas
through absorber 150 into chimney 170 and out of system 100. Fan 140 is
especially configured to blow wet flue gases having low temperatures and
high densities, whereas fan 110 is configured to blow dry flue gases
having high temperatures and low densities. Fans can be configured by
selecting appropriate parameters (e.g., size, power, shape, etc.) to meet
the necessary operational requirements.

[0024] Various sizes and configurations of direct contact
coolers/condensers and CO2 absorbers are known in the art. DCC 130
and CO2 absorber 150 can be configured in any fashion suitable for
removing at least some CO2 from the flue gas.

[0025] Dampers 123, 133, and 153 are provided in various conduits
throughout the system in order to control the flue gas pathway. When
damper 123 is closed and 133 is open, the flue gas travels through FGD
120, DCC 130, absorber 150, and chimney 170. In this manner, both
SO2 and CO2 are removed from the flue gas before leaving the
system and entering the earth's atmosphere. During power production it is
often desirous to shut down CO2 removal processes while continuing
SO2 removal. This can be achieved by closing damper 133 and opening
damper 123, thus allowing the flue gas to pass through FGD 120, conduit
125, and chimney 170 into the atmosphere, while bypassing DCC 130 and
absorber 150.

[0026] It has yet to be appreciated that that various components can be
eliminated from the typical post-combustion system in order to reduce
costs. In particular, prior flue gas treatment processes and systems have
failed to appreciate that fan 140 can be eliminated by configuring fan
110 to provide enough pressure and force to overcome the pressure
resistance in DCC 130 and absorber 150 and blow the flue gas through
absorber 150 and out chimney 170, while still reducing overall power
product costs. By eliminating the need for a second fan, the costs of
various mechanical and electrical systems associated with the second fan
are also eliminated, including maintenance expenses.

[0027] One reason why prior systems have failed to appreciate this
approach is because fans operate more efficiently when moving cold and
condensed gas, as opposed to hot gases. Thus, from a pure
cost-of-operation perspective, it is more efficient to include two fans
wherein one of the fans is located in a cold gas pathway, rather than
merely operating one larger fan in a hot gas pathway. However, due to the
high costs associated with installing and maintaining a second fan, it
unexpectedly turns out that the overall costs will be reduced when one
larger and less efficient fan is used in a hot gas pathway.

[0028] Prior systems and processes have also failed to appreciate that
bypass conduit 125 can be removed from the system and the flue gas can
simply travel through DCC 130 and absorber 150, regardless of whether DCC
130 and absorber 150 are running or shut down. By eliminating the need
for a bypass conduit, various costs associated with the bypass conduit
are eliminated, such as damper 123, entrance to chimney 170, and related
electrical systems. Eliminating the need for these various components
significantly reduces the cost of installing and maintaining the system.

[0029] There are at least two reasons why prior designers of flue gas
treatment systems have failed to appreciate that a bypass conduit can be
eliminated from a post-combustion flue gas treatment system. First,
allowing flue gas to pass through DCC 130 and absorber 150 even when
those components are not in operation prevents personnel from easily
accessing DCC 130 and absorber 150 for maintenance. Second, DCC 130,
absorber 150, and other components downstream of DCC 130 are generally
not configured to withstand hot flue gas conditions and do not meet
National Fire Protection Association (NFPA) codes and standards. Thus,
removing a bypass would require these components to be retrofitted to
meet NFPA code. Despite these disadvantages, it unexpectedly turns out
that the cost savings from removing the bypass is greater than the costs
associated with retrofitting the downstream components. Prior designers
of flue gas treatment plants have failed to recognize and explore this
possibility.

[0030] FIG. 2 shows a post-combustion flue gas treatment system 200, which
is one embodiment of the inventive subject matter taught herein. Unlike
system 100, system 200 does not have a booster fan 140, bypass conduit
125, and dampers 133, 123. Other various related components such as
electrical systems related to the dampers and booster fan (not shown) and
a chimney entrance fitting for a bypass conduit (not shown) have also
been removed.

[0031] Fan 210 of system 200 has been configured to provide more force and
pressure than that provided by fan 110 in system 100, due to the fact
that fan 210 alone must move the flue gas through the entire
post-combustion system, without the assistance of a booster fan 140. By
eliminating the need for a booster fan 140, the costs of fluework,
foundation, motor controls, switchgear, process controls, and other
electrical and mechanical processes associated with a booster fan have
also been eliminated. Thus, while fan 210 will generally consume more
power than fan 110 and fan 140 combined (see FIG. 1) when DCC 230 and
absorber 250 are operating, the overall cost of installing, maintaining,
and operating system 200 has been significantly reduced compared to the
costs of system 100.

[0032] Fan 210 is also configured to operate at different speeds,
depending on whether CO2 removal is performed. When CO2 removal
is not desired, DCC 230, absorber 250, and their related processes (e.g.,
solvent flow to the absorber), are turned off. Since DCC 230 is not
operating to condense water and cool the flue gases and absorber 250 is
not operated to capture CO2, there will be essentially little
pressure resistance created inside DCC 230 and absorber 250 and thus, fan
210 can be set to a lower speed to reduce power consumption. When
CO2 removal is desired, DCC 230 and absorber 250 are turned on and
fan 210 is set to a higher speed.

[0033] Since a bypass conduit has been eliminated from the design of
system 200, flue gases will continue to flow through DCC 230 and absorber
250, regardless of whether CO2 capture is performed. DCC 230,
absorber 250, and other components downstream of the FGD 220 are
configured to withstand the conditions of the hot and wet flue gases
exiting FGD 220. As used herein, "configured to withstand" means
especially configured to resist the structurally destructive properties
of the flue gas (e.g., higher temperatures, thermal expansion, and wet
saturated gas stream, corrosion due to acidity due to the presence of
SO2, SO3, Cl, and other acid gases, and potential deposition
associated with carryover from the desulfurizer 220).

[0034] The conditions of the flue gas exiting the FGD 220 will depend
primarily upon the type of desulfurizer and the fuel. For a low moisture
fuel and a wet desulfurizer, flue gas temperatures at the desulfurizer
exit can be as low as 120° F. For a dry or semi-dry desulfurizer,
flue gas temperatures can range from 20° F. to 50° F.
higher than the adiabatic saturation temperature, resulting in a
130° F. to 200° F. flue gas temperature range. Wet
desulfurizers will also typically produce flue gas having near 100%
humidity conditions having carryover water, ash, and scrubber oils.
Condensed water present in the wet desulfurizer flue gas can have a pH
below 5, and even in the 1-2 pH range, due to trace amounts of acids (Cl,
SO2, SO3, HF, and even CO2) which are frequently present
in flue gases. Dry and semi-dry desulfurizers typically have a humidity
of 50% or higher, and any condensed water will have pH values similar to
that of wet desulfurizer flue gases, due to trace amounts of residual
acids. The dry desulfurizer will typically have much less ash and dust
particles present in the flue gas exiting the flue gas desulfurizer than
a wet desulfurizer, since a fabric filter can be utilized just downstream
of the dry desulfurizer.

[0035] The downstream components are also preferably configured to meet
the standards and codes of the NFPA. By configuring these downstream
components appropriately, the need for a bypass, a second chimney
entrance, dampers, and other related components, has been eliminated.
Thus, even though downstream components in system 200 may require special
adaptations in order to withstand flue gas conditions and meet NFPA
codes, the overall cost of installing, maintaining, and operating system
200 is lower than that of system 100 due to the savings associated with a
simplified design.

[0036] FIG. 3 shows a post-combustion flue gas treatment system 300, which
is yet another embodiment of the present inventive subject matter. System
300 is similar to system 200 except that the induced draft fan has been
relocated to between direct contact cooler 330 and CO2 absorber 350.
Fan 340 is configured to provide enough pressure and force such that the
flue gas exiting a boiler (not shown) is pulled into FGD 320 and DCC 330,
and pushed through absorber 350 and chimney 370, without the need for a
booster fan. When CO2 removal processes are shut down, hot and wet
flue gases will flow through DCC 330, fan 340, absorber 350, and chimney
370. These downstream components have all been configured to withstand
the hot and wet flue gas conditions that are present in flue gases
exiting a desulfurizer. Fan 340 is also configured to operate at
different speeds, depending on whether CO2 capture processes are
turned on or shut off. Unlike fan 210 of system 200, fan 340 is located
downstream of the direct contact cooler. This allows fan 210 to operate
more efficiently than fan 210 when CO2 removal processes are turned
on, since fan 340 will be operating to move cooled and condensed gases.
Thus, system 300 will have lower operating costs than system 200 when
CO2 removal is performed.

[0037] One of ordinary skill in the art will appreciate that system 300
can also be configured to include an induced draft fan just upstream of
FGD 320. In this case fan 340 acts as a booster fan located downstream of
DCC 330. While such a system would not provide all the cost savings of
the present system 300, such a system would provide significant cost
savings over system 100 since the bypass conduit, and equipment
associated with the bypass conduit (e.g., dampers, second entrance to
chimney) are eliminated. By including an induced draft fan, the power
consumption of fan 340 will be reduced since fan 340 can be set to lower
speeds. Such a system can also be configured to turn off one of the two
fans when CO2 removal processes are shut off

[0038] FIG. 4 shows a post-combustion flue gas treatment system 400, which
is another embodiment of the present inventive subject matter. System 400
is similar to system 200, except that system 400 also has a bypass
conduit 425 and dampers 423, 433, and 453. Fan 410 is configured to
operate at different speeds, depending on whether the CO 2 removal
is performed. DCC 430 and absorber 450 can optionally be configured to
meet NFPA codes. Thus, although system 400 does not provide all the cost
savings of 200, system 400 nonetheless provides cost savings over system
100 due to the absence of a booster fan.

[0039] One of ordinary skill in the art will appreciate that there are
physical limitations on fan sizes such that, for large installations, fan
110, 140, 210, 340 and 430 could actually be a set of smaller fans all
positioned is the same position in the gas path.

[0040] Another aspect of the inventive subject matter is a method of
operating a plant by adjusting the speed or vane position of a fan as a
function of whether the direct contact cooler and CO2 absorber are
turned on or shut off depending upon the type of fan (e.g., axial or
centrifugal). The fan is configured to provide sufficient pressure to
move flue gas through the flue gas desulfurizer, contact cooler and
CO2 absorber without the need for a second fan when the direct
contact cooler and CO2 absorber are turned on. When said components
are turned on, the fan can be adjusted to a faster speed or an
appropriate vane position; when said components are shut off, the fan can
be adjusted to a slower speed or the vanes can be repositioned in order
to conserve power consumption.

[0041] Yet another aspect of the inventive subject matter is a method of
simplifying a power plant by (i) configuring a fan to provide sufficient
pressure to move flue gas through a flue gas desulfurizer, direct contact
cooler, and CO2 absorber, without the need for a second fan, and
(ii) configuring the direct contact cooler and CO2 absorber to
withstand flue gas conditions present at the flue gas desulfurizer exit.
Thus, the power plant is simplified by eliminating the need for a second
fan and bypass conduit.

[0042] Those of skill in the art will appreciate that the inventive
concepts disclosed herein can be applied to processes other than SO2
and CO2 removal from post-combustion flue gases. Other gases having
unwanted constituents may be treated and/or conditioned using gas
conditioning units (e.g., absorbers, coolers, desulfurizers, etc.) and
processes that are appropriate for the given application, while still
incorporating the inventive subject matter of this application.

[0043] As used herein, and unless the context dictates otherwise, the term
"coupled to" is intended to include both direct coupling (in which two
elements that are coupled to each other contact each other) and indirect
coupling (in which at least one additional element is located between the
two elements). Therefore, the terms "coupled to" and "coupled with" are
used synonymously.

[0044] It should be apparent to those skilled in the art that many more
modifications besides those already described are possible without
departing from the inventive concepts herein. The inventive subject
matter, therefore, is not to be restricted except in the scope of the
appended claims. Moreover, in interpreting both the specification and the
claims, all terms should be interpreted in the broadest possible manner
consistent with the context. In particular, the terms "comprises" and
"comprising" should be interpreted as referring to elements, components,
or steps in a non-exclusive manner, indicating that the referenced
elements, components, or steps may be present, or utilized, or combined
with other elements, components, or steps that are not expressly
referenced. Where the specification claims refers to at least one of
something selected from the group consisting of A, B, C . . . and N, the
text should be interpreted as requiring only one element from the group,
not A plus N, or B plus N, etc.

Patent applications by Dennis W. Johnson, Simpsonville, SC US

Patent applications by Jonathan Priest, Charlotte, NC US

Patent applications in class Sulfur or sulfur containing component

Patent applications in all subclasses Sulfur or sulfur containing component